Spiral

[Jim Denzler]

I want to extrude a shape along a spiral. My problem is how to create the spiral?
Thanks

[CADTutor]

Jim,

You won't realise how funny this question is unless you've been around here for a while. I'm definately going to do a tutorial on this one day.

Do you mean a SPIRAL or do you mean a HELIX. It's a common error but it does make all the difference.

Either way, it's not possible to create a true spiral or helix in AutoCAD but you can draw an approximation. This can be a really tedious process and so it is usually done with a LISP routine. You'll find such a routine for creating a helix at this topic, http://www.cadtutor.net/forum/viewtopic.php?t=74 I don't have one for a spiral to hand but there must be one about somewhere.

[CADTutor]

Wow, that didn't take long - don't you just love Google.

Here's your spiral lisp routine:

http://www.cadresource.com/library/lispps.html

Have fun and do let us know how you get on.

[Mr T]

Spiral - SOLID Modelling

If it's a spiral as in a cylinderical tube that is like a spring. You draw it like it's manufactured.

A 3D polyline drawn about a 3d solid cylinder, with points drawn on the outside at intervals to SNAP onto.

I do this as a lesson with my school kidz after they have drawn a nut and bolt to create a thread type shape.


Helix - SURFACE Modelling

Similar to above draw a cylinder then points at intervals around the cylinder then a 3D polyline. Copy it and move it up a touch. Then copy
and scale up the 3D polyline so it's got a larger radius then the other two.
Then create a RULE surf (or TAB surf sorry can't remember which one).

Phew !

Anyway they both work. The second one was used by one of my kidz to show a car suspension spring.

Nick

http://www.cadteaching.com

[CADTutor]

Thanks for that Mr.T

I just had a quick look on the old message board and I came across this:

The truth is that it can't be done with perfect accuracy since, as you have discovered, you can't extrude along a 3D spline. However, you can extrude along a 3D Polyline. So, providing you can bear to draw a helix using a 3D polyline, it can be done. Obviously, you only have straight line segments to play with so it can never be perfect. It's the kind of thing that lisp routines are written for. In fact, AutoCAD R12 came with a bonus LISP file called 3dspiral.lsp but sadly it is not included with more recent AutoCADs. However...

you can find one here: http://www.spaug.org/LISP_Index99.Html

...and here: http://www.cadresource.com/library/lispdk.html

This link may also help: http://www.tenlinks.com/CAD/user...screws.htm

and this...

Think about how it works, Here is an example for you.
Set your 3d viewport to SE. Use default UCS.
Start pline at 0,0,0 enter, @100<0,10 enter, @100<90,10 enter, @100<180,10 enter, @100<270,10 enter, @100<0,10 enter, @100<90,10 enter, @100<180,10 enter, @100<270,10 enter,@100<0,10 enter, @100<90,10 enter, @100<180,10 enter, @100<270,10 enter, Press enter to complete the command. Notive how it looks.
You can now use the PEDIT command and SPLINE the helix
I hope it helps you out to try this little exercise.

and this...

You can find 3dspiral.lsp here:

ftp://195.210.176.221/cad/lisp/3DSPIRAL.LSP

thanks to http://www.autocad.ru

...and if anyone knows any more good sources of 3D spiral/helix stuff, post it here and I'll try to pull it all together in a new tutorial.

[Mr T]

You can also have it smoothly curve since it's possible to pedit and FIT a 3D polyline, to fit smoothly between given points eg tangents correct.

Cheers

I'll post up an image of a pupils 'Car Suspension wheel' with one.

Nick

PS 'Mr T' is really my 'Teacher' name

[Mr T]

Aha !

The great spiral debate continues !

Anyway here is an article with a lisp to download free that draws
a similar object.

http://pointa.autodesk.com/local/enu/portal/Articles/article.jsp?articleId=15872

Enjoy

nick

[CADTutor]

OK

maybe I don't need to do a tutorial, it's all there on the pointa article noted in Nicks post. It also included a download of the original spiral.lsp routine shipped with older versions of AutoCAD.

[Mr T]

Yes, no tutorial needed. But how about a tutorial to draw the trees and garden in your 'Lighting/Shadow Tutorial', coz I'll be starting one this week !

It may be interesting to see if we draw things differently or similar. I have moved away from 'surface first then solid' to Solid then add on the surfaces if I really have to.

Why ? well it's easier to edit and manipulate a solid I find.

Although my 'Advanced Higher Graphics Course' stipulates I teach all surfaces(regions) and Solids and their editing/manipulation.

Cheers

Nick

PS Like my wee climbing pic AVITAR ?

[Orbit]

Mr. T

Do you have any idea where the site you mentionate it above http://pointa.autodesk.com/local/enu/portal/Articles/article.jsp?articleId=15872 is?

It looks to me like an index but remember it was a tutorial about a spiral few weeks ago.

[robfowler]

Autodesk has recently rejigged its site and it now seems that saved links now return us to the home page!

From the Autodesk Home Page go to:
Products > AutoCAD > Training (on left menu pane) > See How-to Articles & Tips Links.

I think some of the tips and tutorials have been removed, but I do hope that Autodesk reinstates them. I know that there is increasing pressure for them to do this as folks have got used to the extensive list of tips and tutorials that were there before.

Rob.

[Orbit]

True Rob

I was searching all over that site and the only thing found it about spiral is
http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=2525555&linkID=2475161

No tutorial, no further explanations, nada. I used the lisp and still missing something essential.

[robfowler]

What is it you are trying to do?

Rob.

[Orbit]

I am trying to do a spiral. I followed the lisp prog. but my spiral is flat and in the same plan.
I tried to change the UCS and exploded the spiral to give segments the wanted rotation angle. However, I cannot reach a content result.

[robfowler]

There are 2 spiral lisp routines kicking around that I know of. One is for a 2D spiral (sounds like the one you've got) and the other is for a 3D spiral (helix).

The last one is what you want. I have a copy and can email it to you if you post me your private email address.

Rob.

[Raider]

Can anybody tell me how to post a pic of a drill I did here in autocad? Im new to the forum. I did a helix, copy, rotate and extrude of a twist drill and it turned out ok, I wanted to post it for other people with the same question. I used the helix AutoLISP that member fuccaro had posted, many thanks to him for his help!

[fuccaro]

Welcome Raider!
Follow THIS (http://www.cadtutor.net/forum/viewtopic.php?t=183)link to read about image postings. Here you will find also the rules for the imagine and file sizes -please respect them.

[Raider]

how to I get the pic posted in JPEG or GIF? My Autocad only renders files TIFF, TGA and BMP

[erona]

If you have Photoshop, open them and saveas. Or try this free image conversion software from XNView (http://www.xnview.com/).